1 If you wear glasses or contact lenses, you've probably been to the optometrist for an eye exam. Maybe you bought your glasses or contacts from an optician. An optometrist is someone who does eye exams to see if corrective lenses are needed, and an optician is someone who makes and sells eyeglasses and contacts. Both of these words, optometrist and optician, are forms of the word "optic."2 Optics is the branch of physics that involves the study of light. People who are interested in optics study how light is produced, how it is transmitted, how it is measured, how it is detected, and how it is used. They study the visible light spectrum, which is the rainbow of light that we can see from red to violet. They also study ultraviolet and infrared light, which we can't see.3 Light travels in waves, which are also called electromagnetic waves. Light waves can reflect, refract, and be absorbed. Light reflects when it bounces back off an object. Light reflects off a mirror. When light waves reflect, they bounce back from the surface at the same angle that they hit the surface, in the same way that a billiard ball bounces back from the edge of a pool table. Light refracts when it passes from one material to another and bends. If you put a pencil in a glass of water, you can see where it seems to bend at the surface of the water. Light is absorbed by most objects. A green object absorbs all of the colors except green; it reflects the green light so green is the color that we see. What colors would a red apple absorb? How about a lemon?